Analysis of ground movement rates along the coastline and upper sections of the Ventnor landslide complex was carried out utilizing Persistent Scatterer Interferometric Synthetic Aperture Radar methods using Sentinel-1 SAR data from 2015 to 2019 (four years). Results were compared with rainfall data, historical ground investigation records and monitoring surveys carried out at Ventnor to relate observations to geology, geomorphology and rainfall. Decomposition of InSAR viewing geometries to vertical and horizontal aligned well with previous ground-based studies. Subsidence of −9.8 mm a−1 at the Lowtherville Graben and heave of +8.5 mm a−1 along the coastline south of Ventnor Park were observed. Decomposition to east-west geometry results showed an eastward displacement of approximately 12.4 mm a−1 along the coastline south of Ventnor Park, and a westward displacement of −3.7 mm a−1 throughout built up sections of Ventnor town, indicating the landslide was displacing more in an eastern direction than vertically. The cause of this movement was investigated by using publicly available intrusive boreholes paired with Persistent Scatterer Interferometry, and a new ground model spanning east-west parallel to the coastline was presented. No evidence of significant ground movement was observed along heavily protected sections of the coastline, suggesting coastal defences comprised of concrete aprons and rip rap appear to be an effective coastal management/landslide stabilisation tool when compared to rip rap alone. The mechanism of this increased stability is likely due to the combination of toe weighting and reduced toe erosion. A lag of approximately 13–20 days was observed between high rainfall events and subsequent peaks in ground displacement, which was shorter than a 29 day lag observed in a previous study. Similar observations of prolonged rainfall resulting in prolonged displacements were also observed. The study demonstrates the capabilities of the PSI methodology in identifying the same ground movements that conventional methods provide. By providing detailed analysis of ground deformation of the Ventnor landslide, we demonstrate small ground movements, validated with existing ground movement surveys. Similar methodology can be applied to coastal landslides in urban environments worldwide, providing a relatively cheap and rapid resource for coastal landslide monitoring.
This research investigates small-scale tectonic activity in the Jiujing region in Beishan, northwest China through the application of persistent scatterer (PS) Interferometric synthetic aperture radar (InSAR). PS InSAR is an effective monitoring tool in this unpopulated, arid, and unvegetated rural area, whose surface geology is dominated by a single large granitic intrusion, and which represents a candidate site for a geological disposal facility (GDF) for high-level radioactive waste (HLW) in China. This research demonstrates that faults F16-2, F17, F18, and F20-2 are still active, producing dip-slip motions along the fault planes. The lithological variations in weathering and erosion can be discounted as the cause for these small-scale displacement variations. The work has also identified 11 previously unknown faults, characterising them from vertical (DU) and eastward horizontal (DE) displacements along and across the faults. These newly discovered structures demonstrate how PS InSAR can be used to monitor and measure micro-scale movements on regional-scale faults, which, in many cases, were previously considered to be inactive. Thus, this also improves our understanding of local stress regimes in this area. The Jiujing region is part of a convergent fault zone dominated by NE-SW compression, leading to NE-SW crustal shortening and NW-SE elongation. Through determination of the sense of ground movement measured at irregularly distributed PS points, some faults are reverse and trending NW-SE, while others are normal and trending NE-SW, highlighting how InSAR can be used to resolve fault type and relative movements to monitor tectonic fault blocks at a regional scale.
DInSAR is a remote sensing method of measuring ground deformation over large areas at sub-mm accuracy, and can provide increased insight into geological processes. Analysis of vegetated areas can be highly challenging, due to highly inconsistent radar scattering patterns. PSInSAR was used to measure deformation over the vegetative Salisbury Plain, UK, area. Periods of 6-months and 2-years were separately analysed which revealed complex motion with separate seasonal and tectonic components. Despite a challenging target area, PSInSAR is shown to offer valuable insight into deformation of the Upper Chalk, identifying faults and highlighting differential ground movement thought to be related to groundwater swelling of neighbouring formations and tectonic movement along pre-existing basement faults.
Radar interferometry (InSAR) is a satellite remote sensing technique which offers deformation monitoring at frequent intervals with sub-centimetre accuracy. The most popular form of InSAR monitoring for infrastructure is Persistent Scatterer Interferometry (PSI). This relies on the identification of persistent scatterers: permanent, rigid objects which can reliably backscatter a signal to the satellite receiver. As the typical UK embankment dam has grassed slopes, the majority of persistent scatterers are detected at hard infrastructure located at the dam crest. The aim of this paper is to study the influence of dam features on persistent scatterer detection and quality at Scottish Water embankment dams. Following a case study in which PSI can be shown to detect dam deformation associated with an extreme climate event (the summer 2018 heatwave), statistics from 17 Scottish embankment dams are used to determine which dam features lead to the best quality PSI results. The type of wave protection at the crest of a dam is the biggest influence, whereas the presence of an asphalt surfaced crest road is shown to have a surprisingly limited effect on persistent scatterer quality.
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